Ternary Diamond-Like Compounds and Their Position Among Other Semiconducting Substances

First-principles study on the lattice dynamics and thermodynamic properties of Cu 2 GeSe 3

“…where M is the average atomic mass, θ D is the Debye temperature, δ 3 is the volume per atom, n is the number of atoms in the primitive cell, γ is Grüneisen parameter, and A is a physical constant ≈ 3.1×10 −6 when the units of κ L , M , and δ are taken as Wm −1 K −1 , amu, and angstroms, respectively. The experimental Debye temperature is 168 K [2]. Finally, the obtained lattice thermal conductivity at room temperature is 2.0 Wm −1 K −1 , which is slightly less than the experimental value of 2.4 Wm −1 K −1 [2].…”

“…We note that the polycrystalline sample used in the measurements of Cho et al has lower relative densities, about 95%. This might be the reason that they obtained a lower bulk modulus and a higher thermal expansion coefficient than the earlier experiments [2,5,30].…”

“…The experimental Debye temperature is 168 K [2]. Finally, the obtained lattice thermal conductivity at room temperature is 2.0 Wm −1 K −1 , which is slightly less than the experimental value of 2.4 Wm −1 K −1 [2]. Cho et al ascribed the low thermal conductivity of Cu 2 GeSe 3 to high bonding anharmonicity, based on their estimated Grüneisen parameter of 1.7 [5].…”

“…e h ωn(q)/kB T (e h ωn(q)/kB T − 1) 2 , (2) where h is Planck constant, k B is Boltzmann constant, T is the temperature, and ω n (q) is the phonon frequency of the n-th branch with wave vector q. The calculated C v is 0.328 Jg −1 K −1 at 300 K, which is well consistent with the experimental result of 0.34 Jg −1 K −1 at room temperature.…”

“…The bulk modulus and linear thermal expansion coefficient at various temperatures are calculated within the quasi-harmonic approximation (QHA), in which the phonons are treated as harmonic but volume dependent [23]. The obtained bulk modulus B is 54.0 GPa at 300 K. The experimental Young's modulus for Cu 2 GeSe 3 is E = 91 GPa [2]. Using the relation…”